Catalytic conversion of heavy naphtha fractions



J. A. ANDERSON, JR 2,974,099

March 7, 1961 CATALYTIC CONVERSIONOF HEAVY NAPHTHA FRACTIONS ATTORNEY.

United States Patent CATALYTIC CONVERSION OF HEAVY NAPHTHA FRACTIONS James A. Anderson, Jr., Baytown, Tex., assignor, by mesne assignments, to Esso Research and Engineering Company, Elizabeth, NJ., a corporation of Delaware Filed July 24, 1958, Ser. No. 750,793

7 Claims. (Cl. 20S-6 8) feed stocks such as virgin gas oils or the reforming (e.g.,

over platinum catalyst) of virgin naphtha. Heavy naphtha conversion fractions of this nature have poor volatility characteristics whereby they find only limited utility as components of premium motor fuels.

Thus, for example, thermal cracking of feeds of this nature in the presenceof hydrogen is not satisfactory because the non-selective nature of a thermal conversion process results in the formation of excessive quantities of dry gas and olens and in the provision of a light gasoline boiling range product having only a marginally improved octane number rating. Catalytic reforming is likewise unsatisfactory in that low conversions are realized and in that there is an insufficient inc-rease in octane number rating to make the process economically attractive.

Catalytic hydrocracking of heavy naphtha feed stocks of the above nature over catalysts such as supported cobalt rnolybdate is not satisfactory in that at reasonable operating pressures there is excessive and rapid deactivation of the catalyst whereby it is not possible to obtain a suiicient improvement in octane number rating over prolonged operating cycles.

It has now been discovered that feed stocks of this nature boiling within the range of about 220 to 430 F. may be converted With high yield and good selectivity to highvolatility, high octane number light naphtha fractions -boiling within the range of about 120 to about 350 F. by a catalytic hydrocracking process which is conductedunder specially controlled conditions.

In accordance with the present invention, the catalytic hydrocracking reaction is conducted in the presence of Patented Mar. 7, 1961 a hydrocracking catalyst such as cobalt molybdate supf ported on gamma alumina, silica alumina, etc. and in the further presence of an essentially aromatic diluent having an initial boiling point at least 50 higher than the nal boiling point of the naphtha feed stock, from about l0 to 100 volume percent of diluent being utilized, based on the feed. More preferably, from about 50 to 80 volume percent of diluent is employed. The diluent should be substantially free from hydrogen acceptors.

The aromatic diluent may be obtained from a variety of sources. Thus, aromatic extracts derived from the solvent treatment of petroleum hydrocarbon fractions such as catalytic cracking cycle stock fractions, lubricating oil fractions, etc. which contain in excess of 50 volume percent and normally in excess of about volume percent of aromatics may be employed.

The hydrocracking conditions to be employed should suitably include a temperature within the range of about 850 to 950 F., a liquid hourly space velocity (for the naptha feed stock) within the range of about 0.5 to about 1 v./v./hr., a pressure within the range of about 300 to about 950 p.s.i.g., and a hydrogen charge rate within the range of about 200 to about 6000 standard cubic feet of hydrogen per barrel of total naphtha and diluent feed stock. For best results it is preferable to utilize a tem-` perature within the range of about 900 to about 950 F., a space velocity within the range of about 0.7 to about 1.0 v./v./hr., a pressure within the range of about 700 to about 950 p.s.i.g., and a hydrogen charge rate within the range of about 500 to 2000 cubic feet of hydrogen per barrel of total feed.

The naphtha hydrocarbon feed stock which is treated in accordancev with the present invention is a converted naphtha fraction boiling within the range of about 220 to about 430 F. and, more preferably, within the range of about 350 to 430 F.

lt is a feature of the present invention that the naphtha feed stock is substantially free from components boiling below about 220 F. in that such components have an adverse eilect with respect to the production of maxi. mized amounts of light high octane number naphthas.

The invention will be further illustrated with respect to the accompanying drawing wherein the single figure is a schematic ow sheet illustrating a preferred method of practicing the process of the present invention.

Turning now to the drawing, there is schematically shown a catalytic cracking zone 10, such as a uidized catalytic cracking zone, to which a suitable feed stock such as a virgin gas oil feed stock is charged by way of a line l2. A gas oil boiling range recycle fraction 14 obtainable in a manner to be described subsequently may be admixed with the virgin feed charged to the catalytic cracking zone 10 if desired.

Within the catalytic cracking zone 10 the gas oi-l feed stock is contacted with ya suitable cracking catalyst Ysuch as a silica alumina cracking catalyst under Vcata-lytic cracking conditions whereby at least a portion of the fee'd stock is converted to lower boiling more valuable prod:

ucts. The hydrocarbon products from the catalytic cracking zone are charged by way of a line 16 to a suitable fractionation zone 1S. For purposes of conveniences, the fractionation zone 18 has been shown as a single distillation column. It will be understood, of course, that in actual practice the fractionation zone i8 may comprise a plurality of distillation towers, together with suitable auxiliary equipment in order to obtain satisfactory recovery and fractionation of the products of the catalytic cracking zone 10.

By way of example, within the fractionation zone i8 the products from the catalytic cracking zone may be fractionated to provide a gaseous overheads fraction 20 containing hydrogen and normally gaseous C1 to C4 hydrocarbons. There may also be provided a high octane number light naptha fraction 22 and a heavy naptha frac tion 24 boiling Within the range of about 220 to about 430 F. and, more preferably, within the range of about 350 to about 430 F. There may also be obtained heavier distillate fractions such as a heating oil fraction 26, a gas oil boiling range fraction 28 and a bottoms fraction 29.

The heavy naptha fraction 24 obtained from the catalytically cracked petroleum hydrocarbons will normally be characterized by comparatively low octane number and a comparatively low volatility whereby it is of only limited utility. However, in accordance with the present invention, the heavy naptha fraction 24 is further treated in order to improve the properties thereof in a catalytic hydrocracking zone 30 in the presence of a suitable hydrocracking catalyst such as gamma alumina supported cobalt molybdate in the presence of added hydrogen and aromatic diluent.

The aromatic diluent may be obtained, for example, by subjecting the gas oil boiling range recycle fraction 2S to solvent extraction in an extraction zone 32 in the presence of a solvent such as liquefied sulfur dioxide, liqueed normally gaseous hydrocarbons such as propane, butane, etc. which will selectively remove aromatics from the recycle fraction 28.

Thus, for example, the fraction 28 may be charged to a solvent extraction tower adjacent the top thereof for countercurrent contact with a suitable solvent such as liquefied sulfur dioxide introduced adjacent the bottom of the tower by way of a line 34. A rainate fraction 36 comprising a solvent solution of extracted oil may be withdrawn from the top of the ltower 32 and charged to a stripper 38 for the removal of solvent through an overheads line 40. The thus-treated oil may suitably be Withdrawn from the stripper 38 by way of a recycle line 14 for further treatment in the catalytic cracking zone 10 in the above-described manner.

An extract fraction 42 which may contain residual amounts of solvent is withdrawn from the bottom of the extract tower 32 and charged to a stripper 44 wherein solvent is removed overhead by way of the line 46. The aromatics extract (which may contain from about 85 to 95 volume percent of aromatics and boil within the range of about 600 to about 900 F.) may be withdrawn from the bottom of the stripper 44 by way of a withdrawal line 4S controlled by a valve 50 leading to the charge line 24 for the catalytic hydrocraclting reactor 30. in this fashion the aromatic diluent and the heavy naptha fraction required for successful operation of the catalytic hydrocracking zone 30 may be simultaneously prepared by the catalytic cracking of gas oil fractions.

As has been indicated above, from about 10 to 100 volume percent of the heavy aromatic diluent 48 is admixed with the heavy catalytic naptha 24 to be charged to the catalytic hydrocracking zone 30. Excess aromatic diluent may be discharged from the system by way of a discharge line 52 controlled by a valve 54.

The mixture of heavy naptha and aromatic diluent is charged to the hydrocracking zone in the presence of added hydrogen. The hydrogen may be obtained, for

4 example, from an extraneous source and may be charged by a line 56 controlled by a valve 58. Alternately, all or a portion of the hydrogen required for the catalytic hydrocracking process may be obtained by charging the gaseous overheads fraction 20 from the fractionation zone 18 to a `separator 60 wherein the fraction is separated into a normally gaseous fraction discharged by way of a line 62 and a hydrogen rich fraction discharged by way of a line 64 controlled by a valve 66 leading to the charge line 24 for the catalytic hydrocracking zone 30.

The hydrocracking conditions to be employed within the hydrocracking zone 30 have been set forth above and include a temperature within the range of 850 to 950 F., a liquid hourly space velocity for the catalytic naphtha within the range of about 0.5 to about 1.0 v./v./ hr., a pressure within the range of about 300 to about 950 psig., and a hydrogen charge rate within the range of about 200 to about 6000 cubic feet of hydrogen per barrel of total feed (catalytic naphtha and diluent).

Within the catalytic cracking zone 30, the naphtha feed stock is at least partially converted to a high octane number high volatility light naphtha fraction.

The products from the catalytic hydrocracking zone 30 are discharged by Way of a line 68 leading to a fractionation zone 70 of any suitable construction and cornprising one fractionation tower (as shown) or a plurality of fractionation towers, together with auxiliary equipment. Within the fractionation zone 70, the products may be fractionated to provide a normally gaseous overheads fraction discharged by line 72 controlled by a valve 74, such fraction containing hydrogen and minor amounts of dry gas, such as methane, formed during the hydrocracking reaction. If desired, all or a portion of the normally gaseous fraction 72 may be recycled to the hydrogen charge line 56 by way of a recycle line 76 controlled by a valve 78.

There is also recovered a first distillate fraction comprised essentially of butanes and pentanes and a substantial yield of a light naphtha fraction 82 boiling within the range of about 125 to about 350 F. or, if desired, within the range of about 125 to about 220 F.

There is also obtained from the fractionation zone 70 a heavy naphtha fraction 84 boiling within the range of about 220 to about 430 F. and, more preferably, within the range of about 350 to about 430 F. A heavy fraction 86 boiling within the boiling range of the diluent is recovered by way of a discharge line 86 controlled by a valve 87. There is also obtained a bottoms fraction 88.

The diluent boiling range fraction S6 may be discharged from the system or, if desired, may be recycled by way of a recycle line controlled by a valve 92.

In 'accordance with one form of the present invention, the catalytic hydrocracking zone, after being initially placed onstream, is supplied substantially exclusively with recycle diluent, the valve 50 in the line 48 being closed after start-up operations are complete. A comparatively small amount (about 5 to l0 volume percent) of the heavy naphtha charge stock to the catalytic cracking zone 30 is converted into a highly aromatic material boiling within the diluent boiling range. Thus, in continuous operations, a minor amount of diluent boiling range material will be continuously discharged from the system by opening the valve 87 as required. Thus, the aromatic diluent initially supplied to the hydrocracking zone 30 by way of the line 48 will gradually and progressively be replaced by a diluent formed in situ by the catalytic hydrocracking of the heavy naphtha feed stock.

The invention will be further illustrated with respect to the following specific examples which are given by way of illustration and not as limitations on the scope of this invention.

In conducting the following-described experiments, the catalyst employed consisted essentially of l5 weight percent of oxides of cobalt `and molybdenum supported on gamma alumina, the catalyst being employed in the form of a xed bed of catalyst in aV reactor provided with suitable means for the preheating of naphtha feed stock, aromatic diluent, and hydrogen to the desired reaction admixed in the ratio of '2 parts by volume of diluent with 3 parts by volume of heavy catalytic naphtha. Thev mixture was charged to the reactor at a temperature of about 925 F., a pressure of about 750 p.s.i.g., together temperature. In addition, a premixer was provided for with 1000 cubic feet of hydrogen per barrel of total intimately admixing the naphtha feed, the aromatic diluliquid feed material (diluent plus naptha). The charge ent, and hydrogen prior to their introduction into the rate was about 1.5 v./hr./v. (0.6 v./hr /v. diluent plus reactor. Freshly sampled natural gas blanketed feeds 0.9 v./hr./v. naphtha). For comparative purposes, runs were utilized in all experiments. The spent catalyst from Were made under the above-described reaction conditions each experiment was washed with benzene and benzene with a charge material consisting of the heavy naphtha, was thereafter evaporated therefrom prior to testing of the heavy naptha agaln being charged at the rate of the catalyst samples for surface area and combustible 0.9 v./hr./v. to provide a direct comparison. The carbon. The feed stock for the experiment and the results that were obtained are set forth in the following diluent had the properties set forth in the following table. table.

Table II Feed Type of Operation Diiuent Non-Diiuent Run number. T-210-1 T-210-2 T-212 T212A Hours on Catalyst 0-32 33-57 0-18 19-62 Yields, Vol. Percent of Feed: (1) (l) Dry Gas (Wt. Percent of Feed) 15. 2 12. 8 8.1 7. 6 or-l-o. 10. 0 11.0 7. 5 6. 3 125-350 F 46. 7 44. a 33. 0 19. s 350430 F 92 0 02. 2 es. 7 46. 2 62. 0 430 F.+. (so. 7) (2s. o) 6.1 a. 4 Total or 100.0 88.2 91.0 92.8 92.5 Octane Numbers:

Eiective RON 2 9s. 4 97. 2 99. 1 99. s 130 95 0 99. s 9s. 4 103. 4 101. 5 Effective MON 2- 125-35o 92.5 95.5 87.6 89.1 asm-430 F- s3. 6 93. 0 90. 2 94.1 Bromine Number:

1.7 2.o 9.1 51.0 asv-430 F 1s. 2 1.1 2.0 4. s 11.2

Fresh Used Used Catalyst Inspections: Surface Area, M.2/Gm 173.0 100.2 0.4 Carbon, Wt. Percent. 13. 8 23. 8

and dry gas yieris) i +3 Voi. percent tetraethyl lead.

Table I FEED STOCK INSPECTIONS Fraction of Light SO2 Description Heavy Catalytic Kerosene Catalytic N aphtha Extract Naphtha Distillate Inspections:

Boiling Range, F Total Total 450 F Vol. Percent of Feed.. 100.0 P 35. 3 350 355 356 358 360 361 363 365 867 370 374 95 880 FBP., F 396 Percent Recovery. Percent Loss-- FIA Analysis- Aromatics, Vol. Percent 6 .9 17.0 84.8 Olefins, Vol. Percent..- 18. 3 60. 4 7.0 Saturates, V01. Percent- 20.8 22. 6 8.2 Sulfur, Wt. Percent 0.16 0.10 0.09 Bromlne No., cgJgm. 20. 4 104.0 1. 5 MSA Optical Density-..

EXAMPLE I increase in bromine number during the latter portion ofthe non-diluent experiment. In addition, with respect to volatility improvement; the run conducted in the presence of a diluent provided for an almost constant rate of volatility improvement (measured as the total volume of C4-350 F. product) whereas there was'a material decline in volatility improvement with respect to the non-diluent run. Still further, with respect to the catalyst inspections, it will be noticed that'the unregenerated catalyst at the end of the 57-hour diluent run still had a surface area of about 100 meters per gram and containedV 13.8 weight percent of carbon whereas with the non-diluent run the cata# lyst was substantially completely deactivated, having a surface area of 0.4 m.2/ gm.

With respectto motor octane number improvement, it

`will be noted that the diluent operation provided for a much moreY eiective productmthafn the nonfdiluent separation, the research octane numbers of the diluent and In the iirst of a series of runs, the aromatic kerosene non-diluent products being substantially equivalent.r

EXAMPLE II higher temperature of about 975 F. was employed.A The Y results that were obtained are set forth in Table III.

Table III EXAMPLE IV As has been indicated, the naphtha feed stock for the Type o, Operation ufff Duuent Nm present mvenuon should preferably be free from naphtha R N b Diluent 5 components boiling below about 220 F. This is illus- Hrslflcgiggtjj 21:11: 1.31421? 'l Hated by the results that were obtained when charging a hght catalytic naphtha boiling primarily within the M VOLPercentomeed: range of about l25 to about 300 F. to the reactor in Dry Gas (Wt. Percent) 10.8 9.5 the absence of d1luent and in the presence of about 1000 333g cubic feet of hydrogen per barrel of feed stock at a 51.7 47.2 temperature of about 975 F. and a pressure of about 96:? F/'50 p.s.i.g. at a charge rate of about 3 v./hr./v. The octane Numbers: results that were obtained are set forth in the following Eiiectlve RON 2- t b1 125-350f'1r 99.6 101.8 a e' 4M0O 05,0 100.9 103.0 From Table V 1t will be observed that the selectwity e@ 5Y3508 8&0 2 6 Of the feed stock to motor fuel products was poorer in 35 t\1 -43 0 83.6 01.6 01.0 this situation than in the preceding examples, there being Olnamt 2M ,9 5 a considerable loss of material boiling within the range 350-430 18.2 9.2 7.8 of about 125 to 220 F. and no substantial improvement 1n the overall quality of Ithe product material boiling Fresh Used Used within this range. Still further, there was a decrease in Catalyst Inspecteurs; research octane number with respect to products boiling urfce size alQ/I/Gn 173.0 1.2 1.1 below about 250 F. lt will be observed that, while not I on me 23'7 23'3 reported in the table, at the end of the run, the catalyst had a surface area of about 13.0 meters per gram (173 l o mblgrgsiaggggeldgfiymm indicates duuent con 2o meters per gram fresh) and contalned about 23 percent 2 +3 Vol. Percent tetraetbyl lead. 0f Carbon.

From Table 1H it will be observed that unsatisfactory These results demonstrate that it is undesirable to inresults were obtained with both the diluent and nondud@ Substantl quantities 0f naphha boilitlg below diluent type operation in that in each instance the catalyst bOU 220 F 111 me feed Stock l0 the Caalylc hydlO was substantially completely deactivated. Cl'aCkmg steth Having described my invention, what is claimed is: EXAMPLE HI l. A method which comprises subjecting a non-virgin In another series of runs, employing the naphtha and hydrocarbon feed stock boiling within the range of about diluent of Example I, the operating conditions included .35 220 to about 430 F. to catalytic hydrocracking condia temperature of 925 F., a hydrogen charge rate of tions in the presence of a iixed bed of hydrocracking about 1000 cubic feet of hydrogen per barrel of total catalyst in a catalytic hydrocracking zone under conver feed, a charge rate of about 1.5 v./hr./v. (1.0 v./hr./v. sion conditions including a temperature Within the range naphtha feed rate and 0.5 v./hr./v. diluent feed rate). of abou-t 850 to about 950 F. and a pressure within However, in this situation, the pressure that was utilized 40 the range of about 300 to 950 p.s.i.g. in the presence of was about 220 p.s.i.g. The results that were obtained about i0 to 100 volume percent of an essentially aromatic are set forth in Table IV. hydrocarbon diluent boiling within the range of about Table IV Feed Type of Operation Diluent Non-Diluent Run Number T246 T-242 Hours on Catalyst 5-20 2h32 5-20 21-32 Yields, Vol. Percent oi Feed: (1) (l) Dry Gas (Wt. Percent of Feed) 3. 8 2. 7 8.1 6.9 4.7 2.7 7.3 6.1 58. 3 57. 52. 7 64. 5 35. 7 37. 5 29. 1 29. 2 (4 2) (1.0) 3.8 3.0 94. 5 96. 2 92.9 92. s Octane Numbers:

E'ective RON 2- 125350 F 98.0 97.2 96.7 97.1 97.5 350-430 F.- 92.7 97.8 93.9 98.4 95.9 Effective MON 125850F 85.4 36.0 83.8 92.0 87.4 350-430F 82.0 86.5 84.3 92.3 84.9 Bromine Number:

Fresh Used Used Catalyst Inspections:

Surface Area, M.2/Gm 173.0 5.2 24.7 Carbon, Wt. Percent.. 20. 8 18. 5

1 Dilnent-free basis (negative 430 F.+yleld indicates diluent contribution to gasoline and dry gas yields).

2 +3 Vol. percent tetraethyl lead.

From Table IV it Will be observed that unsatisfactory results were again obtained in that there was a rapid deactivation of the catalyst, in this situation the catalyst being deactivated most rapidly in the presence of the diluent.

450 to about 900 F. and about 200 to 6000 cubic feet of hydrogen at a napbtha feed stock charge rate of about 0.5 to about l v./hr./v. and recovering from the products of said hydrocracking step a high octane low volatility Table V OATALYTIO HYDROORAOKING OF LIGHT OATALYTIO NAPHTHA Feed Run Number T244 Hours on Catalyst 3-14 15-32 Yields, Vol. Percent of Feed:

Dry Gas (Wt. Percent). 16. 1 11. 1 5. 4 18.6 13. 6 39. 4 25. 7 30.6 25.0 16.0 18.8 19. 2 12. 9 14. 3 9. 6 7.1 7. 0 1.4 2. 6 3. 1 100.0 82. 9 87. 4

RON MON RON MON RON MON Eiectlve Octane Numbers 1 12 -200 F 101. 5 85. 2 97.2 90.4 98. 4 85. 5 with f= 4. 1. 65 2. 85 200-250 F 99.8 88.3 98. 4 88. 2 99.1 85.1 with f= 3. 1. 65 2. 25 250300 F 97. 2 86. 3 101.5 90. 6 98. 4 85. 8 with f= 2. 1. 30 1. 65 300350 F 95.1 83.7 102. 4 91. 9 97.6 84.6 with f= 1. 80 1. 25 1. 30

Bromine Number:

125- 128 47.8 97. 3 104 35. 8 63. 3 72 17. 4 47. 2 3 F 44 10. 8 33. 2 FIA Aromatics,

1 +3 Vol. percent tetraethyl lead.

naphtha fraction boiling within the range of about 120 to about 330 F.

2. A method as in claim 1 wherein the hydrocracking conditions include a temperature within the range of about 900 to about 950 F., a space velocity within the range of about 0.7 to `about 1.0 v./hr./v., a pressure within the range of about 700 to 950 p.s.i.g., and a hydrogen charge rate within the range of about 500 to 2000 cubic feet of hydrogen per barrel of total feed.

3. A method as in claim 1 wherein the feedstock is a naphtha fraction obtained by the catalytic cracking of a gas oil boiling range hydrocargon and wherein the diluent is an aromatics extract obtained by the selective extraction of aromatics from a gas oil boiling range hydrocarbon produced by the catalytic cracking of a petroleum hydrocarbon gas oil fraction.

4. A method for treating the products obtained from the catalytic cracking of a hydrocarbon gas oil fraction which comprises the steps of recovering from the products of catalytic cracking a heavy naphtha fraction boiling within the range of about 220 to 430 F. and a heavier fraction boiling Within the range of about 450 to 900 F., subjecting said heavier product traction to solvent extraction in the presence of a solvent for the selective removal of aromatics to thereby provide an aromatics extract fraction boiling within the range of about 450 to 900 F., admixing from about 10 to 100 volume percent of said aromatic extract fraction with said heavy naphtha fraction and charging the resultant mixture to a catalytic hydrocracking zone containing a bed of a supported cobalt molybdate catalyst in the presence of about 200 to 6000 cubic feet of hydrogen per barrel of mixture under hydrocracking conditions including a temperature Within the range of about 850 to 950 F. and a pressure within the range of about 300 to about 950 p.s.i.g. at a naphtha feed stock charge rate within the range oi about 0.5 to 1 v./hr./v., and recovering from the products of said catalytic hydrocracking step a naphtha traction boiling within the range of about 120 to about 350 F.

5. A method as in claim 4 wherein the hydrogen for the catalytic hydrocracking step is recovered from the products of catalytic cracking.

6. A method as in claim 5 wherein there is additionally recovered from the catalytic hydrocracking step an aromatics fraction boiling within the range of about 450 to about 900 F. and wherein said aromatic extract fraction initially derived from said products of catalytic cracking is replaced by said heavyl aromatic fraction recovered from said catalytic hydrocracking step.

7. A method for treating the products obtained from the catalytic cracking of a hydrocarbon gas oil fraction,

which comprises the steps of recovering from the products of catalytic cracking a heavy' naphtha raction boiling within the range of about 350 to 430 and a heavier fraction boiling Within the range of about 450 to 900 F., subjecting said heavier product fraction to solvent extraction in the presence of a solvent for the selective removal of aromatics to thereby provide an aromatics extract fraction boiling within the range of about 450 to 900 F., admixing from about 50 to 80 volume percent of said aromatic extract fraction with said heavy naphtha fraction and charging the resultant mixture to a catalytic hydrocracking zone containing a bed of a supported cobalt molybdate catalyst in the presence of about 500 to 2000 cubic feet of hydrogen per barrel of mixture under hydrocracking conditions including a temperature within the range of about 900 to 950 F. and a pressure Within the range of about 700 to about 950 p.s.i.g. at a naphtha feed stock charge rate within the range of about 0.7 to 1 v./v./hr., and recovering from the products of said catalytic hydrocracking step a naphtha fraction boiling Within the range of about to about 350 F.

References Cited in the file of this patent UNITED STATES PATENTS 2,697,684 Hemminger et al Dec. 21, 1954 2,768,937 Anderson et al Oct. 30, 1956 2,889,264 Spurlock June 2, 1959 

7.A METHOD FOR TREATING THE PRODUCTS OBTAINED FROM THE CATALYTIC CRACKING OF A HYDROCARBON GAS OIL FRACTION WHICH COMPRISES THE STEPS OF RECOVERING FROM THE PRODUCTS OF CATALYTIC CRACKING A HEAVY NAPHTHA FRACTION BOILING WITHIN THE RANGE OF ABOUT 350* TO 430*F. AND A HEAVIER FRACTION BOILING WITHIN THE RANGE OF ABOUT 450* TO 900*F., SUBJECTING SAID HEAVIER PRODUCT FRACTION TO SOLVENT EXTRACTION IN THE PRESENCE OF A SOLVENT FOR THE SELECTIVE REMOVAL OF AROMATICS TO THEREBY PROVIDE AN AROMATICS EXTRACT FRACTION BOILING WITHIN THE RANGE OF ABOUT 450* TO 900* F., ADMIXING FROM ABOUT 50 TO 80 VOLUME PERCENT OF SAID AROMATIC EXTRACT FRACTION WITH SAID HEAVY NAPHTHA FRACTION AND CHARGING THE RESULTANT MIXTURE TO A CATALYTIC HUDROCRACKING ZONE CONTAINING A BED OF A SUPPORTED COBALT MOLYBDATE CATALYST IN THE PRESENCE OF ABOUT 500 TO 2000 CUBIC FEET OF HYDROGEN PER BARREL OF MIXTURE UNDER HYDROCRACKIG CONDITIONS INCLUDING A TEMPERATURE WITHIN THE RANGE OF ABOUT 900* TO 950*F. AND A PRESSURE WITHIN THE RANGE OF ABOUT 700 TO ABOUT 950 P.S.I.G. AT A NAPHTHA FEED STOCK CHARGE RATE WITHIN THE RANGE OF ABOUT 0.7 TO 1 V../V./HR., AND RECOVERING FROM THE PRODUCTS OF SAID CATALYTIC HYDROCACKING STEP A NAPHTHA FRACTIOIN BOILING WITHIN THE RANGE OF ABOUT 120* TO ABOUT 350*F. 